Currently, the touch input devices are widely used. According to the conventional touch input technologies, the touch input devices include sensors based on a resistance and sensors based on a capacitance, i.e. the touched position on the touch input device is identified by measuring the electrical potential changes via a circuit. Recently, the optical touch input technology is developed, the touched position is identified by identifying the optical images. For the optical touch input device, the information can be entered by writing on a specific coding arrangement via a light pen, wherein the specific coding arrangement is fabricated on the substrate of the optical touch input device. The coding arrangement is exposed to the light emitted from the light pen, and then the light is reflected to the image-detecting system. Then, the coding is obtained by identifying the detected images, so that the optical touch input is effected.
The cholesteric liquid crystal has a structure similar to the cholesterol molecule. It has spirally oriented stick-like molecules. As like the “nematic liquid crystals” with chiral characteristic. The molecules in the different layers of the cholesteric liquid crystal orient at a slight angle relative to each other, so that the cholesteric liquid crystal has a spiral structure.
Due to the optical activity and the spiral structure of the cholesteric liquid crystals, the light become the right-circularly polarized wave or the left-circularly polarized wave when reflected from the cholesteric liquid crystals. The 50% of the light with the optical activity identical to that of the cholesteric liquid crystals is reflected. The wavelength of the reflected light is equal to the average index of refraction of the cholesteric liquid crystals multiplied by the pitch length of the cholesteric liquid crystals. Accordingly, the cholesteric liquid crystals are widely used duo to the high index of refraction thereof. For example, U.S. Pat. No. 6,753,044 B2 discloses a coloring media including cholesteric liquid crystal flakes has the improved reflection characteristics of the red, green and blue colors.
Up to now, the brightness, contrast, the reaction time and the cost of the liquid crystal display stilled should be improved. The U.S. Pat. No. 6,727,967 B2 discloses a half-transmission color liquid crystal display, wherein a phase retardation plate and a liquid-crystal layer are provided between a polarizing plate and a cholesteric liquid crystal layer. In the U.S. Pat. No. 6,727,967B2, when the liquid crystal display device functions as a reflective liquid crystal display, light entering through the polarizing plate is reflected by the cholesteric liquid crystal layer; however, when the liquid crystal display device functions as a transmission liquid crystal display, light from the backlight passes through the cholesteric liquid crystal layer, and thereby the brightness and the color density of the liquid crystal display device are improved.
The present invention provides a liquid crystal panel with reflective coding patterns and a liquid crystal display with reflective coding patterns, wherein the optical touch input technology and the cholesteric liquid crystals are integrated into a panel or a display to be a touch input apparatus.